@staticsafe IMO the problem is that people expect you to reply immediately. Read receipts reinforce that expectation, but it can happen nevertheless.
OTOH, some chat cultures (notably IRC) developed the approach of send-and-go-on-with-your-life, as the person may reply after 30 minutes or 2h or sth.
Another thing that would be IMO useful is presence statuses. Back in early IM days, you had:
wanna-talk, online, brb, bbl, busy, invisible, disconnected
it helped set expectations for response time